In U.S. Pat. No. 3,447,479, as well as many other sources of technical literature, parenteral solution infusion pumps are disclosed in which a reciprocating syringe or other volume varying device is in communication with a chamber having upstream and downstream one-way valves, each positioned to permit flow only in the downstream direction. When this structure is made part of a parenteral solution administration set, reciprocation of the syringe back and forth at a controlled rate can result in the administration of precisely controlled amounts of parenteral solution to the patient.
A danger of this type of structure exists, in that a pumped syringe administration set will pump air as readily as it will pump liquids, the result of which can be fatal for the patient. As a result of this, "air eliminator" units, for example those described in Rosenberg U.S. Pat. No. 3,523,408, have been proposed to vent air from the set, to prevent its administration to the patient.
These air eliminator units comprise a porous, hydrophobic membrane and a porous, hydrophilic membrane, generally closely spaced together, in which the hydrophobic membrane communicates with the exterior of the administration set, and the hydrophilic membrane functions as a brrier across the flow path of the set.
However, if the hydrophilic membrane barrier is defective, the air eliminator device will be inoperative, and air can be pumped into the patient with potentially fatal results.
A need therefore exists for a fluid-pumping structure, capable of use in an administration set, which prevents the pumping of air, and which is fail-safe, in that any membrane rupture in the device will not result in the pumping of air to the patient.
Also, it is desirable for administration sets to be completely closed from the exterior, so that there can be no contamination through failure of a membrane or the like.
There also is a need for a safe administration set which can pump viscous solutions and solutions containing particulate matter, such as blood, elemental diet solutions, and other solutions having undissolved solids in suspension, such colloids, which might tend to clog the hydrophilic filter of a conventional air eliminator set.
The invention of this application provides a pump device which can be incorporated in a parenteral solution set, a blood administration set, or the like, having the above advantages over the apparatus of the prior art. The pump apparatus structure of this invention can also be used for other purposes in which it may be desired to pump liquid while preventing the pumping of gas.